yay

It's interesting that they have 2 internal candidates, but they're asking you to come in for a second interview. I suspect they think you're a better fit than those 2 candidates, as usually an employer will prefer an internal candidate over an external one. (It's easier and cheaper to train someone who's been working there for a while. Plus, the employer already knows the an internal person's work ethic.) So, if they didn't think you were that good, they would have gotten rid of you by now. That's my opinion anyway.

It sounds like you're in really good standing!

Whether or not you get the job, it's impressive that you got to the 2nd round. That's an accomplishment on its own.